Luna Sea (stylized as LUNA SEA) is a Japanese rock band formed in Kanagawa Prefecture in 1986. Due to the use of makeup and costumes early in their career and their widespread popularity, they are considered one of the most successful and influential bands in the visual kei movement. Throughout the mid-1990s they used significantly less makeup, and after a one-year break in 1997, came back with a more mainstream alternative rock style and toned down their on-stage attire. They disbanded in 2000. In 2003, HMV ranked Luna Sea at number 90 on their list of the 100 most important Japanese pop acts.

Initially founded in 1986, by bassist J and rhythm guitarist Inoran while in high school, the band was originally called Lunacy. In 1989 they recruited lead guitarist Sugizo, drummer Shinya and vocalist Ryuichi, a lineup that has remained the same. They released a few demo tapes prior to renaming themselves Luna Sea and releasing their self-titled debut album in 1991. The band achieved their breakthrough success with a sold-out tour in 1991, which helped them get a contract with MCA Victor, and with the release of their second album Image (1992), which reached number nine on the Oricon music chart. Following the critically acclaimed albums Eden (1993), Mother (1994) and Style (1996), the band switched to Universal in 1998 and released their best-selling studio album, Shine. In late 2000, after their seventh studio album Lunacy, Luna Sea disbanded.

Luna Sea reunited for a one-off reunion concert in 2007 at the Tokyo Dome, and again in 2008 for the hide memorial summit. In 2010 the group officially reunited and held a world tour. Three years later they released their first new album in thirteen years, A Will. Their ninth album, Luv, followed four years later in 2017. At the end of 2019, their tenth album Cross, co-produced by Steve Lillywhite, became their first to top Billboard Japan.

High school friends, Jun "J" Onose and Kiyonobu "Inoran" Inoue founded a band called Lunacy in 1986. Three years later, on January 16, 1989, they recruited drummer Shinya Yamada from the band Pinoccio, who insisted that his bandmate Yasuhiro "Sugizo" Sugihara also join. As J was already the bass player and Inoran preferred to play rhythm guitar, Sugizo switched from bass guitar to lead guitarist. They played a single concert before firing their vocalist for a lack of talent. Ryuichi Kawamura (then called "Rayla") from the band Slaughter then joined on May 6, finalizing the group's lineup. Lunacy debuted on stage at the 100-seat capacity Play House in Machida, Tokyo on May 29, 1989. They released their first demo tape, "Lunacy", on August 9, with all one hundred copies sold out. In October, they transferred their activities to Meguro, where they performed at local venues such as Rock-May-Kan and Live Station. In December, the band's second demo "Shade" was released, with all one thousand copies sold out, and on December 17 the band sold all 150 tickets for their first official one-man live concert at Machida Play House.

In 1990, Lunacy continued to play small venue concerts and for the first time outside Tokyo, in Osaka. They held their first anniversary concert Kurofuku Gentei Gig (黒服限定GIG; "dress code black gig") at Machida Play House on June 10, where they distributed the free demo "Lastly". Towards the end of the year, the band changed their name from Lunacy to Luna Sea. In early 1991, they were discovered by hide of X Japan and were signed by X Japan co-founder Yoshiki to his independent label Extasy Records. They then took part in the label's Nuclear Fusion Tour in March with Gilles de Rais and Sighs of Love Potion. On the tour, a 3-track sample CD including a song from each band was freely distributed, to which they contributed a short sample of "Precious". Their first album, the self-titled Luna Sea, was released the following month. They held larger live performances throughout the year with their first national tour titled Under the New Moon, which was separated into three legs or "Episodes", with 45 performances, of which the final concerts attracted an audience of over one thousand. The tour gathered seventeen thousand people in total. On October 29, they performed at that year's Extasy Summit concert, at the sold out Nippon Budokan.

In January 1992, the band's official fan club Slave was launched. In March they held a small fan club tour and on May 20 performed their last indie concert, the third kurofuku gentei gig at Machida Play House. On May 21, Luna Sea released their first major studio album, Image, on MCA Victor. The album peaked at number 9, spending 14 weeks on the Oricon charts. It was followed by the band's debut tour Image or Real in May, and corresponding with their increasing popularity, continued with After the Image tour in September. There were 25 concerts with an audience of more than twenty-eight thousand people. On October 31, they performed at another Extasy Summit at the Nippon Budokan.

Luna Sea's first single, "Believe", was released in February. The single peaked at number 11, spending 7 weeks on the charts. The band started working on their second album and began touring throughout the country for it on April 16, with the Search for My Eden tour. The tour included 14 concerts in the same number of locations, and mobilized an audience of around twenty-six thousand people. The album Eden was released on April 21, and peaked at number 5, spending 19 weeks on the charts. It was certified gold, for shipment of over two hundred thousand copies, by the RIAJ. In July they released their second single "In My Dream (With Shiver)", which peaked at number 9 and spent 4 weeks on the charts. In August, the four concert Search for My Eden Encore tour was held, of which the latter two shows on August 26 and 27 were planned for the Nippon Budokan. However, the last concert was postponed until August 30 because of the Category 4 Super Typhoon Yancy. In December the Sin After Sin video compilation was released, which included performances from smaller venues during the year, and the band started the Garden of Sinners 93-94 tour, with 20 concerts that mobilized forty thousand people. At the end of the year, the band received the "Grand Prix New Artist of the Year" award at the 7th Japan Gold Disc Awards.

On February 12, 1994, the band performed the tour's final concert at the sold-out 17,000 seat Yokohama Arena. On July 21, their third single "Rosier" was released. It peaked at number 3, spent 25 weeks on the charts, and was certified gold by the RIAJ. In December, the single's promotional video was awarded the "Best Promotional Video" at the 36th Japan Record Awards. Between August 9 and 30, the band went on a sold-out five-stop tour with Soft Ballet and Buck-Tick titled LSB. It is now looked at as a legendary tour in Japanese rock, not only due to the three headlining acts coming together, but because the then up-and-coming guest acts, The Yellow Monkey, L'Arc-en-Ciel, The Mad Capsule Markets and Die in Cries, all went on to achieve success. On September 21, Luna Sea released their fourth single "True Blue", which topped the charts, and was certified platinum for selling over four hundred thousand copies. Responding to the popularity, the band released their third album Mother on October 26. It peaked at number 2, spent 30 weeks on the charts, and eventually sold more than half a million copies. In December they performed at the Osaka-jō Hall, and three times, of which two were consecutive, at the Nippon Budokan.